The present invention relates to a power reception control device, a power reception device, an electronic instrument, and the like.
In recent years, non-contact power transmission (contactless power transmission) which utilizes electromagnetic induction to enable power transmission without metal-to-metal contact has attracted attention. As application examples of non-contact power transmission, charging a portable telephone, a household appliance (e.g., telephone handset), and the like has been proposed.
JP-A-10-225020 discloses a non-contact power transmission device, for example. The technology disclosed in JP-A-10-225020 aims at providing a small non-contact power supply device which can supply power to a plurality of loads, and utilizes a plurality of induction coils.
According to the technology disclosed in JP-A-10-225020, an induction coil and a rectifier circuit are provided in a portable electronic instrument which receives power, and a secondary battery (e.g., lithium-ion battery) is charged using the output voltage of the rectifier circuit.
In recent years, a secondary battery such as a lithium-ion battery or a lithium polymer battery has been widely utilized as a battery for a portable terminal such as a portable telephone or a notebook type personal computer. A secondary battery such as a lithium-ion battery or a lithium polymer battery has an advantage in that the energy density is extremely high as compared with other batteries. On the other hand, since a secondary battery requires strict charge control taking deterioration and safety into consideration, highly accurate charge management technology is necessary.
Therefore, it is preferable to charge a secondary battery using a charging circuit utilizing a regulator (e.g., series regulator) which enables highly accurate output control.
It is desirable that the charging time of a secondary battery be short taking convenience to the user of a portable terminal into consideration. However, the charging efficiency of a secondary battery when using non-contact power transmission is lower than the charging efficiency when using a normal charger (charger using an AC adaptor) so that the charging time tends to increase. Therefore, when charging a portable terminal using non-contact power transmission, it is important to reduce power loss during charging as much as possible.
The inventors of the invention has found that power loss of the regulator occurs when it is necessary to cause a large amount of charging current to flow (e.g., when charging a secondary battery which has been exhausted to a large extent). This may hinder a reduction in charging time. It is also desirable to minimize heat generation of the regulator during charging taking the safety of a portable terminal into consideration.